Lecithin-sphingomyelin ratio, also known as L-S or L/S ratio, is the major cause of fetal lung maturity. It is also used as an indicator of fetal lung maturity.
The lungs are one of the important organs in the body; the lungs require surfactant to lower the pressure of the alveoli in the lungs. Surfactant is a mixture of protein, lipids, glycoproteins, lecithin, and sphingomyelin. The lecithin places an important role in the surfactant because it makes the mixture more effective.
The movement of pulmonary secretions from the fetal lungs into the amniotic fluid helps to maintain a balance between lecithin and sphingomyelin. To test for fetal lung maturity, amniotic fluid is collected via amniocentesis, and the sample is spun down in a centrifuge at 1000 rpm for 3–5 minutes. Thin-layer chromatography (TLC) is performed on the supernatant, which separates out the components.